Generally, as a printing apparatus which prints words, numbers, barcodes and the like on a recording medium such as a label or a paper wound in a roll shape (hereinafter referred to as a paper roll) with an ink ribbon, there is known a thermal printer which is called as a label printer or a barcode printer.
With a ribbon roll wound in the rolled shape being set on a delivering shaft, the ink ribbon is wound on a winding reel mounted on a ribbon winding shaft through a certain ink ribbon conveyance path. A platen roller and a thermal head are arranged opposite to each other and across the ink ribbon in the ink ribbon conveyance path. Further, the paper roll mounts a delivering reel on a holder, and the front end of the paper roll is guided from the conveyance roller section to pass through the space between the platen roller and the thermal head to discharge to the outside from a paper discharging opening. The paper roll is overlapped with the ink ribbon between the platen roller and the thermal head, and a printing is carried out through a thermal transfer which is realized by heating the ink ribbon using the thermal head and transferring the melted ink to a paper.
However, in a case of printing with an ink ribbon, an ink ribbon may be cut off or a white blank occurs during a printing. It is considered that one of the reasons for the occurrence of this phenomenon generally lies in the adhesion of a paper roll to the ink ribbon, which sometimes occurs when the ambient temperature of a printing apparatus is high. Especially, the quality of an ink ribbon cannot be guaranteed if ambient temperature is high, and it tends to an adhesion when the paper roll is returned for a given length during a reverse feeding. At this time, the adhesion caused by the contact of the paper roll to the ink ribbon based on the thermal head can be found here and there.